The new Nightforce NX8 looks like it was built to fill the same market at the existing Vortex HD AMG. They are smaller in terms of objective lenses (50mm) and main tubes (30mm) and also overall length at 13/14".
They have the same light weight (28oz) and therefore benefits to the long range hunter, they are almost the same street pricing.
They have similar features and build quality. They are both First Focal Plane (FFP).
The Nightforce is built in Japan and slightly shorter and has a wider magnification range, the Vortex is built in the USA and arguably has better glass - although we can't see the difference.
These are both excellent scopes for those wanting a shorter, lighter weight but long range scope for any activity they choose, the only downside is at this time they both only have a small reticle choice.
However, NF is adding in several more choices by winter 2019 including PRS style and Horus reticle designs.